Metal-glass joint



Nov. 18, 1947 Y o; PREssz-:L ET AL METAL-GLASS vJOIT Filed April ll, 1945 f ,uniud atented Nov. 18, 1947 METAL- GLASS JOINT Otto Pressel and Gerardus Adrianus Marinus Diepstraten, Carshalton, England, assignors to The Hartford National Bank & Trust Company, Hartford, Conn., as trustees Application April 11, 194,5, Serial No. 587,690 In Great Britain February 3, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires February 3, 1964 9 Claims.

More particularly in the manufacture of electric vdischarge tubes, it is frequently desired to produce a vacuum-tight joint between a glass component and a metal component. In general, due to differences in the coefficients of thermal expansion, a direct joint between the metal component, consisting for instance of copper, and the glass component is not durable, particularly when the joint is expo-sed to appreciable changes in temperature', e. g. becomes heated during the operation of the tube, as for instance when the metal component is the anode of an X-ray tube. One technique which is adapted to overcome this diiiculty is to provide between the metal component and the glass component an intermediate metal component consisting of an alloy having a coefcient of thermal expansion not substantially different from that of the glass component and of a character permitting the production of a fused joint with the glass, the other end of the intermediate member being secured to the `metal at a sleeve joint, `by any convenient method such as welding `or soldering. The provision of such an intermediate member is found to safeguard the glass component adequately, but in some 'cases the intermediate member itself which generally is made relatively thin-walled so as to impart the desi-red iiexibility tocompensate for the differences in thermal expansion of the glass and metal components, is found to fracture or crack adjacent the metal component.

The object of the present invention is to avoid or at least to minimise the occurence of such failure of the Vintermediate member in joints of this kind.

According to the present invention, the intermediate member is associated with the metal component in such manner that the surface of contact between the metal component and the intermediate member lies in a surface which is inclined to the axis of the metal component, e. g. in the surface of a cone, the aXis of which is coincident with the axis of the metal component, the angle Aof the cone being large. In this way stresses in the intermediate member adjacent the metal component in a direction at right angles to the contact surfaceare wholly or largely eliminated. Preferably, the end of the intermediate member is accommodated in a recess in the periphery of the metal member and is secured therein by a suitable solder or lute. Preferably the solder *or the like forms a layer or cushion between the intermediate member and the walls of the recess. In order to .locate the intermediate member in relation to the metal `component, provision may be made for contact between (Cl. Z50-27.5)

hem at three or more points at the bottom of the recess.

The manner in which the invention may be employed for sealing an anode in an X-ray tube is illustrated by way of example in the accompanying drawings in which:

Fig. l is a side view, partly in section, of the anode end of an X-ray tube,

Fig. 2 is a section substantially along the 'line II-II of Fig. 1,

Fig 3 is a view corresponding to Fig. l, :but showing only the anode assembly ofan alternative construction.

Considering rst the embodiment of Figs. l and 2, the cathode I and anode 2 are enclosed within the glass envelope 5. The cathode l may be of any conventional form and is not shown in detail. The anode 2 as shown is of the kind provided with a hood 3 furnished with a window 4 for the passage of the Y-ray beam. The joint between the glass envelope 5 and the anode 2, which customarily consists of copper, is produced with the use of an intermediate sleeve 6 consisting of a metal alloy of coefficient of thermal expansion not materially different from that of the glass envelope 5. The intermediate member 6 is directly sealed to the glass envelope 5. For securing the other end of the member 6 to the stem 'l of the anode 2, the stem 'l is provided with a shoulder 8 which forms part of a spherical surface and which is generally inclined to the axis of the stem 'l towards 'the target surface of the anode. The intermediate member '6, which can be regarded as a cylindrical sleeve terminating in a heini-spherical cup with a central aperture for 'the passage of the stem l is positioned adjacent the shoulder 8 and thereafter ra sleeve or ring 9 is placed against the outer face of the intermediate member 6. The curvatures of the spherical faces of the shoulder and ring 9 are so chosen that the end of the member 6 is accommodated in a recess of substantially constant width. On the outside of the ring 9 is mounted a washer I0 which serves to locate vthe X-ray tube in relation to its support. rIhe end of the intermediate member 6 is secured in the recess formed between the shoulder 8 and the ring 9 by a layer of solder Il which lls this recess. Preferably the end of the intermediate member 6 does not extend throughout to the bottom of the recess, but is spaced away from -it except at a smallnumber of locating points formed by projections I2 (Fig. 2) which extend to the bottom of the recess.

In the alternative construction of Fig. 3, in which the parts identical with those already described with reference to Figs. 1 and 2 are muicated by the same reference numerals, the shoulder I3 on the anode stem 'I is inclined away from the target surface of the anode 2 and forms part of a conical surface of large angle. The angle between the axis and the generatrix of the conicalsurface may approximate to 90. The ring I4 forming the other wall of the recess has its cooperating surface formed on a similar conical surface so as to produce a parellel-sided recess to receive the end of the intermediate member I5. As in the first embodiment the intermediate member I5 is secured by solder II and preferably the intermediate member I5 contacts the bottom of the recess only at a few spaced points in a manner similar to that described with reference to Fig. 2. In Fig. 3 the intermediate metal member I5 is not sealed directly to the main envelope of the X-ray tube, but is sealed to an intermediate glass sleeve I6, the free end of which is sealed to the envelope in the final assembly.

With glass of the nature usually employed for the manufacture of X-ray tubes, the intermediate member can be made of an alloy consisting predominantly of iron, nicke1 and cobalt with possibly small amounts of manganese and carbon, typical proportions being 54% Fe, 28% Ni, 18% Co. Examples of such alloys are those available commercially under the trade names Kovar and Fernicof We claim:

1. A metal-glass joint consisting of a glass component, an intermediate component directly sealed to the glass and made of a metallic material having a, coeiiicient of thermal expansion not substantially different from that of the glass component, and a metal component to which the intermediate component is sealed in such manner that two surfaces of contact are provided between the metal component and the intermediate component which surfaces lie in parallel surfaces which are inclined to the axis of the metal component.

2. A metal-glass joint consisting of a glass component7 an intermediate component directly sealed at one end to the glass and made of a metallic material having a coefficient of thermal expansion not substantially different from that of the glass component, and a metal component to which the intermediate component is sealed, a recess formed between a shoulder on said metal component and a metal sleeve positioned on said metal component, the other end of said intermediate component being tapered so as to be received in said recess, the outside surface of the said intermediate component being sealed to the said shoulder of the said metal component and the inside surface sealed to the said sleeve.

3. An electric discharge tube comprising a glass envelope and a joint in accordance with claim 2 between said envelope and the anode.

4. A metal-glass joint consisting of a glass component, an intermediate component directly sealed to the glass and made of metallic material having a coefficient of thermal expansion not substantially diierent from that of the glass component, and a metal component to which the intermediate component is sealed in such manner that the surfaces of contact between the metal component and the intermediate member lies in the surfaces of cones of large angle the axes of which are coincident with the axis of the metal component.

5. A metal-glass joint consisting of a tubular 4 glass component, an intermediate tubular metal component directly sealed to the glass and made of material having a coefficient of thermal expansion not substantially different from that of the glass component and terminating in an openended tapering section, a metal component having in its surface a recess adapted to receive the open end of said tapering section, a sleeve positioned on said metal component and a sealing material securing said open end in said recess between the said metal component and said sleeve.

6. A metal-glass joint according to claim 5, wherein the sealing material forms a cushion between the intermediate member and the walls of the recess.

7. A metal glass joint consisting of a tubular glass component, an intermediate tubular metal component directly sealed to the glass and made of material having a coefficient of thermal eXpansion not substantially diierent from that of the glass component and terminating in an openended tapering section, a metal component having in its surface a recess adapted to receive the open-end of said tapering section with the end thereof spaced from the bottom of the recess except at a number of spaced locating points, a sleeve positioned on said metal component, and a sealing material securing said open end in said recess between the said metal component and the said sleeve.

8. A metal-glass joint comprising a tubular glass component, an intermediate tubular metal component made of material having a coeiiicient of thermal expansion not substantially different from that of the glass sealed directly to the glass and terminating in an open-ended tapering section, a metal component having a portion adapted to pass through the open end of said tapering section and a shoulder adapted to abut against the tapering section adjacent the open end, and a sleeve fitting that part which passes through and adapted to abut against the other face of the tapering section adjacent said open end, whereby a sealing space is formed between said sleeve and said shoulder to receive said open end and sealing material for sealing the outside surface of the said open end to the said shoulder and the inside surface to the said sleeve.

9. An electric discharge tube comprising a glass envelope and a joint in accordance with claim 8 between said envelope and the anode.

OTTO PRESSEL. GERARDUS ADRIANUS MARINUS DIEPSTRATEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,210,699 Bahls Aug. 6, 1940 2,147,418 Bahls Feb. 14, 1939 1,880,571 Wellman Oct. 4, 1932 2,279,831 Lempert et al Apr. 14, 1942 2,327,586 Altee Aug. 24, 1943 FOREIGN PATENTS Number Country Date 574,500 Great Britain Jan. 8, 1946 OTHER REFERENCES Electronics, October 1940, page 30. (Copy in Division 54.) 

